21989873 has 2 divisors, whose sum is σ = 21989874. Its totient is φ = 21989872.

The previous prime is 21989861. The next prime is 21989879. The reversal of 21989873 is 37898912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21967969 + 21904 = 4687^2 + 148^2 .

It is a cyclic number.

It is not a de Polignac number, because 21989873 - 2¹⁰ = 21988849 is a prime.

It is a super-2 number, since 2×21989873² = 967109029112258, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21989879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10994936 + 10994937.

It is an arithmetic number, because the mean of its divisors is an integer number (10994937).

Almost surely, 2^21989873 is an apocalyptic number.

It is an amenable number.

21989873 is a deficient number, since it is larger than the sum of its proper divisors (1).

21989873 is an equidigital number, since it uses as much as digits as its factorization.

21989873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 217728, while the sum is 47.

The square root of 21989873 is about 4689.3360937344. The cubic root of 21989873 is about 280.1609321452.

The spelling of 21989873 in words is "twenty-one million, nine hundred eighty-nine thousand, eight hundred seventy-three".